/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.cors.reactive;

import java.net.URI;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;

/**
 * Utility class for CORS reactive request handling based on the
 * <a href="http://www.w3.org/TR/cors/">CORS W3C recommendation</a>.
 *
 * @author Sebastien Deleuze
 * @since 5.0
 */
public abstract class CorsUtils {

    /**
     * Returns {@code true} if the request is a valid CORS one.
     */
    public static boolean isCorsRequest(ServerHttpRequest request) {
        return (request.getHeaders().get(HttpHeaders.ORIGIN) != null);
    }

    /**
     * Returns {@code true} if the request is a valid CORS pre-flight one.
     */
    public static boolean isPreFlightRequest(ServerHttpRequest request) {
        return (request.getMethod() == HttpMethod.OPTIONS && isCorsRequest(request) &&
                request.getHeaders().get(HttpHeaders.ACCESS_CONTROL_REQUEST_METHOD) != null);
    }

    /**
     * Check if the request is a same-origin one, based on {@code Origin}, and
     * {@code Host} headers.
     *
     * <p><strong>Note:</strong> as of 5.1 this method ignores
     * {@code "Forwarded"} and {@code "X-Forwarded-*"} headers that specify the
     * client-originated address. Consider using the {@code ForwardedHeaderFilter}
     * to extract and use, or to discard such headers.
     *
     * @return {@code true} if the request is a same-origin one, {@code false} in case
     * of a cross-origin request
     */
    public static boolean isSameOrigin(ServerHttpRequest request) {
        String origin = request.getHeaders().getOrigin();
        if (origin == null) {
            return true;
        }

        URI uri = request.getURI();
        String actualScheme = uri.getScheme();
        String actualHost = uri.getHost();
        int actualPort = getPort(uri.getScheme(), uri.getPort());
        Assert.notNull(actualScheme, "Actual request scheme must not be null");
        Assert.notNull(actualHost, "Actual request host must not be null");
        Assert.isTrue(actualPort != -1, "Actual request port must not be undefined");

        UriComponents originUrl = UriComponentsBuilder.fromOriginHeader(origin).build();
        return (actualScheme.equals(originUrl.getScheme()) &&
                actualHost.equals(originUrl.getHost()) &&
                actualPort == getPort(originUrl.getScheme(), originUrl.getPort()));
    }

    private static int getPort(@Nullable String scheme, int port) {
        if (port == -1) {
            if ("http".equals(scheme) || "ws".equals(scheme)) {
                port = 80;
            } else if ("https".equals(scheme) || "wss".equals(scheme)) {
                port = 443;
            }
        }
        return port;
    }

}
